Process for the comminuting of smokeless powder of the nitrocellulose type



Patented June 17, 1924.

UNITED STATES V 1,498,053 PATENT OFFICE.

GERALD H. MAINS, OF DETROIT, MICHIGAN, AND FRED B. STIEG, 0F CHEVY CHASE,

MARYLAND.

PROCESS FOR THE COMMINUTING OF SMOKELESS POWDER OF THE NITROCELLUIAOSE TYPE.

No Drawing.

To all whom it may concern:

Be it known that we, GERALD H. MAINS and FRED B. STIEG, citizens of the United States of America, and residents of Detroit, Wayne County, Michigan, and Chevy Chase, Montgomery County, Maryland, respectively, have jointly invented a certain new and useful Process for the Comminuting of Smokeless Powder of the Nitrocellulose Type, of which the following is a specification.

This invention relates to a process for comminuting, or reducing various sized grains of nitrocellulose, or so-called smokeless, powders to a fine state of subdivision and. has particular application to the utili zation of furfural as a softening agent in comminuting such powders.

Smokeless powder deteriorates with age and becomes unfit for military purposes. It may, however, be converted into a useful form for explosive and other purposes by comminuting the grains, that is, reducing them to a finely divided or powdered condition. Heretofore, this has been customarily accomplished by grinding, or crushing and grinding the grains of powder Without preliminary softening. Because of the hard, tough, and horny nature of the grains, the comminution has required a great deal of power and consequent expense. In addition thecomminuation has involved an explosive and fire hazard even when conducted under water.

We have found that by immersingthe rains of nitrocellulose powder in a treat- 1ng solution composed of furfural, ethyl alcohol, and water in certain proportions that a softening action is exerted on the grains which swell and absorb furfural, alcohol, and water, but do not become gelatinous or sticky. When the powder has become entirely softened throughout, it may be readily disintegrated by almost any of the well known grinding processes, ball mill treatment, or treatment in a beater. The disintegrated powder is freed from the absorbed solvents by washing with water. The powder may then be dried by the usual processes. Thedried powder is in a very fine uniform condition and may be used in various ways, for example, (1) to make up new sizes of smokeless powders by gelatinization p with a suitable agent, (2) alone or mixed Application filed September 17, 1923.- Serial No. 663,285.

with other ingredients to form blasting and explosive powders, or (3) to serve as a base for lacquers and varnishes, and for artificial leather and similar products.

The proportions of furfural, ethyl alcohol, and water that may be used successfully in the treating solution are included within a comparatively limited range. The

proportions must of course first meet the requirements of complete miscibility of the three components so that only one liquid layer is present in the mixture. Furthermore if the proportion of furfural presentis too high or of the water too low, the grains will be still more swollen, and p rtly or wholly gelatinized, and will become sticky and diflicult to disintegrate. If no water or only a very small pro ortion of water is present the powder wil entirely dissolve in the furfural or furfural and alcohol mixtures. On the other hand, if the proportion of the furfural is too low or of the water too high the grains are only partially softened and can not be readily disintegrated. The relation between the proportionsof water and furfural present is of greater importance than the proportion of each in the solution considered separately. For best results the proportion of furfural present should be from 4 to 5 times that of the water although furfural-water ratios between the limits of 2:1 and 8:1 may be used with, some degree of success.

In order to obtain a treating solution which will have the desired softening effect the proportions of the various ingredients must be included approximately within the following limits: The proportion of furfural by weight should be not greater than 85 per cent nor less than 15 per cent of the total solution; the proportion of water by weight should be not less than 2 per cent nor greater than 24 percent of the solution; the ratio of the proportion of furfural to that of water should not be greater than 8 to 1 nor less than 2 to 1; and the proportion of ethyl alcohol used in each case should be the difference between the sum of the proportions of furfural and water used and 100 per cent.

We have obtained the best results by using the following proportions by weight: 29.2 er cent of furfural, 64.1 per cent of ethyl alcohol, and 6.7 per cent of water. In this case the ratio of furfuralto water is about 4.4 to 1. It should be noted that toward the extremes of the limits the grains will tend to become either gelatinous and sticky or else be only partially softened. Proportions approaching the optimum ones given are perfectly miscible at room temperature. Where the proportions are toward the outer range of the limits the temperature may in some cases have to be considerably increased in order to bring about complete miscibility.

When using the foregoing optimum proportions a quantity of treating solution equivalent to from 2 to 6 times the weight of the powder grains may be used with fairly good results, although we have found a ratio of solution to powder of about 4 to 1 to give the most satisfactory softening effect in preparing the powder for me chanical disintegration.

The process is ordinarily carried out at room temperature. The length of time required for complete softening depends upon the size of powder being treated. For surplus smokeless powder of the common millimeter gun size 20 to 24 hours soaking in the treating solution at room temperature is sufli'cient. For the large 15 inch gun size, 20 days may be needed for complete softening. Increase of temperature speeds up the softening somewhat but it is doubtful whether it is more economical to apply heat during the softening period or to use more treatment tanks and carry out the softening at roomtemperature.

The mechanical disintegration of the softened grains is preferably carried out in the presence of a small excess of the treating solution, in order to prevent loss by evaporation of the liquids absorbed in the grain and consequent partial drying or hardening of the grain. A large excess of the treating solution should be avoided, since after the subsequent drowning of the powder in Water, more solvent would have to be recovered by distillation processes.

The removal of the absorbed solvents from the disintegrated powder is accomplished by stirring into a large excess of water, so-called drowning the powder. The use of hot or nearly boiling water, especially as a second wash, facilitates the removal of the solvents.

An alternative method which may b conveniently used to treat the softened powder is to drain off the excess treating liquid, and force the powder under pressure through fine openings or perforations near which revolves a brush to break up the threads thus formed. It should be noted that the softened grains are not in a gelatinous condition and neither are the threads formed from them. The broken threads may be passed directly into water to remove the absorbed furfural and alcohol. If

the resulting powder is not sufficiently fine for the purpose desired, it may be quite readily ground since it is in an amorphous and non-gelatinous condition. Ordinarily it is preferable to use the method of mechanical disintegration first described by which a very fine state of subdivision is readily obtained and by which explosive risk is eliminated owing to the presence of the excess treating solution.

In order that the process may be more clearly understood the following examples of preferred ways in which we carry-out our process are given:

1. A weight of 200 kilograms of surplus smokeless powder of 75 mm. gun size containing about 98 per cent by weight of nitrocellulose is placed in a tank together with 800 liters of a solution containing 29.2 parts of furfural, 64.1 parts of ethyl alcohol, and 6.7 parts of water by weight. This treating solutionmay be readily made up by mixing together 192 liters of technical furfural (containing about 95 per cent furfural by Weight) and 608 liters of commercial 95 per cent ethyl alcohol (about 92.6 per cent ethyl alcohol by weight). The tank is covered and the powder allowed to soak for 20 to 24 hours at room temperature, about 20 to 30 (3., when the powder is completely softened. The softened powder and liquid are run into a beater such as is used in treatment of paper pulp and there disintegrated until a sample drowned in water settles out as in a uniformly fine condition. The powder in the heater is allowed to settle, most of the treating solution decanted, and the wet powder run slowly into a tank of water fitted with a stirrer, using about 20 liters of water to 1 kilogram of powder. After stirring for 5 to 10 minutes, the powder is allowed to settle, the water and extracted solvents decanted and hot water near the boiling point run in with additional stirring using 10 to 20 times as much water as powder. This second wash water is decanted and the powder drained, partially freed from water in a centrifuge, and dried in a current of warm air. The decanted solution from the heater is brought up to the original concentration by addition of the proper amounts of furfural or alcohol as determined by analysis and reused for treatment of a second batch of powder. The first and second wash waters are mixed and run through a column still to recover the furfural and alcohol.

2. On a small scale we often prepare batches of comminuted powder by placing 200 grams of 75 mm. type smokeless powder in a flask with 900 cc. of a treating solution containing 30 per cent of furfural, 63 per cent of alcohol and 7 per cent of water by weight, and allowing the grains to soak for 24 hours at room temperature. The average diameter of the powder increases from about 0.133 inches to 0.220 inches. The softened powder together with about half of the unabsorbed treating solution, is ground up in a mortar or small ball mill and drowned in 4: liters of water; It is stirred for a few minutes and filtered in a large Buchner funnel. The wet the powder is forced through the holes in the form of threads which are quite brittle. The nozzle is held against a revolving brush and the finely broken threads are collected in a jar of water. The water is drained ofi and. the powder washed in hot water and dried. This powder is then in the form of particles about 0.02 inches in diameter which may be directly used for regelatinization or which may be ground still finer in a mortar. 3. One way by which we comminute the large cylinders of smokeless powder used for'15 inch guns is to place 2.6 kilograms of the powder in a small tank with 3.8 liters of technical furfural and 14 liters of 95 per cent (by volume) ethyl alcohol. The grains are allowed to soak for about 20 days at room temperature when the grains are softened throughout. We place the liquid and powder in a ball mill and stop the mill when a sample shows a fine enough state of subdivision. The excess treating solution is decanted, and the powder stirred into 50 liters of water. The liquid is decanted from the powder and 25 liters of hot water added. The powder is then drained and dried.

From a consideration of the process it appears that furfural is the principal softening agent, water the agent that prevents or retards gelatinization, and ethyl alcohols diluting and carrying agent for the other two liquids. ()ther organic liquids which are non-solvents for nitrocellulose and are miscible with both furfural and water may alone or in mixtures serve as the diluting and 1. A composition of matter for use in preparing smokeless powders of the nitrocellulose type for mechanical comminution comprised of a liquid solution composed of furfural as a softening agent,'water as a gelatinization preventing agent, and an organic liquid, which is a non-solvent for nitrocellulose and which is miscible with both furfural and water, as a diluting and carrying agent.

2A composition of matter for use in preparing smokeless powders of the nitrocellulose type for mechanical comminution comprised of a liquid solution composed of furfural as a softening agent, water as a gelatinization retarding agent, and ethyl alcohol as a diluting and carrying agent.

3. A composition. of matter for use in preparing smokeless powders of the nitrocellulose type for mechanical comminution comprised of a single liquid phase solution of furfural, ethyl alcohol and water, in which the proportion of furfural by weight is not greater than 85 per cent nor less than 15 per cent, in which the proportion of water by weight is not less than 2 per cent nor greater than 24 per cent, and in which the ratio of the proportion of furfural to that of water is not greater than 8 to 1 nor less than 2 to 1.

4. A composition of matter for use in preparing smokelesspowders of the nitrocellulose type for mechanical comminution comprised of 29.2 parts of iurfural, 64:.1 parts of ethyl alcohol, and 6.7 parts of water by weight.

5. The step in the process of comminuting smokeless powder of the nitrocellulose type consisting in preparing the grains of powder for mechanical disintegration by treating them with a solution cantaining furfural as a softening agent, water as a gelatinization preventative, and an organic liquid, non-solvent for nitrocellulose and miscible with water and furfural, as a carrying and diluting agent.

6. The step in the process of comminuting smokeless powder of the nitrocellulose type consisting in preparing the grains of powder for mechanical disintegration by treating them with a solution containing furfural as a softening agent, water as a gelatinization preventative, and ethyl alcohol as a carrying and diluting agent.

'3'. The step in the process of comminuting smokeless powder of the nitrocellulose type consisting in preparing the grains of powder for mechanical disintegration by treating them with a solution of furfural, ethyl alcohol, and-water in which the proportion of furfural by weight is not greater than 85 per cent nor less than 15 per cent, in which the proportion of water by weight is not less than 2 per cent nor greater than 24 per cent, and in which the ratio of the proportion of furfural to that of water is not greater than 8 to 1 nor less than 2 to 1.

8. The step in the process of comminuting smokeless powder of the nitrocellulose type consisting in preparing the grains of powder for mechanical disintegration by treating them with 4 to 5 times their weight of a solution containing 29.2 parts of furfural, 64.1 parts ofethyl alcohol, and 6.7 parts of water by weight.

9. The step in the process of comminuting smokeless powder of the nitrocellulose type comprising the mechanical disintegration of the grains of the powder previously softened by treatment with a solution composed of furfural as a softening agent, water as a gelatinization preventing agent, and an organic liquid, which is a non-solvent for nitrocellulose and which is miscible with both furfural and water, as a diluting and carrying agent, the said mechanical disintegrationtaking place in the presence of an excess of the treating solution,

10. The step in the process of comminuting smokeless powder of the nitrocellulose type comprising the forcing of the grains, previously softened by treatment with a solution composed of furfural as a softening agent, water as a 'gelatinization preventing agent, and an organic liquid, which is a nonsolvent for nitrocellulose and which is miscible with both .furfural and water, as a diluting and carrying agent, through small openings in such manner as to form nongelatinous threads suitable for subsequent mechanical disintegration in the presence of water. a

11. The product resulting from the process I of comminuting smokeless powder of the nitrocellulose type in which process the grains of powder are first softened by treatment with a solution composed of furfural as a softening agent, water as a gelatiniz'ation preventin'g agent, and an organic liquid, which is a non-solvent for nitrocellulose and which GERALD H. MAINS. FRED B, STIEG.

Witnesses:

J. L. CARR, A. MCNAUGHT. 

